Traditional clock radios display time information, receive radio frequency (RF) signals for FM and AM radio use, and contain an audible radio or buzzer alarm for alerting the user at preprogrammed and predetermined times. More advanced clock radio devices incorporate computers, televisions, compact disk players, audio cassette players, and sleep and snooze alarm features and functions.
While useful in many respects, traditional clock radios are unsuitable for many users because they rely solely upon an audible alarm to alert the user. For example, a conventional audible alarm incorporated within a clock radio device is of little or no value to those users who happen to be hearing impaired or completely deaf. Moreover, while audible alarms may be perfectly capable of alerting the primary user at the desired alarm time, they can also be obtrusive and annoying to others who may be asleep in a common or proximate berthing area and desire to awaken at a later time than the primary user. In such situations, the primary user wishes to ensure that the alarm volume is sufficient to awaken himself at the predetermined time, but often an alarm volume sufficient for that purpose also disturbs others who happen to be asleep in the common or proximate berthing area.
Alternative designs for silent awakening devices have previously been contemplated. For example, U.S. Pat. No. 4,093,944 to Muncheryan (hereinafter `Muncheryan`) describes the design for a clock that can transmit an RF signal to a "pocket pager" unit that contains a vibrating mechanism. While undoubtedly useful, the device described in Muncheryan does not address the possibility that the "pocket pager" may fail to receive the RF alarm signal and therefore fail to wake the user. All antennas display directivity and gain characteristics, so RF transmissions are relatively weak in certain directions with respect to the transmitting antenna. Reception quality therefore depends upon the location of the receiving antenna with respect to the transmitting antenna associated with the clock. Reception of RF transmissions is also relatively weak when the polarization of the receiving antenna differs from the polarization of the transmitting antenna. Therefore, reception quality also depends upon the orientation of the receiving antenna with respect to the transmitting antenna. Destructive interference is another phenomenon which threatens the reception capability of the receiving unit. Radio waves may take different paths to arrive at the receiving unit. If the waves are out of phase when they arrive, the alarm signal will be destroyed. The receiving unit will also fail when its power source is depleted. Conventional battery indicator lights are helpful in alerting users when a degraded power source condition exists and prompting them to replace or charge the receiving unit battery, however, users may fail to identify or inadvertently ignore the warning if the warning is received when the user is tired or asleep. Failure to alarm at a predetermined time, whatever the mode for the failure, is a "false negative" alarm failure.
Further, prior art silent awakening devices do not address the problem of "false positive" alarms. A false positive alarm occurs when the silent awakening unit vibrates (silently alarms) at a time other then the desired preset alarm time. Prior art devices utilize pulsed RF transmission to activate a vibrating mechanism in the receiving unit; therefore, the reliability of the receiving units are susceptible to external sources of electromagnetic radiation. Thus, local broadcasts or noise at the same frequency could activate the vibrating mechanism in the receiving unit.
Many prior art alarm clock radios provide the user with a "snooze function." When the desired preset alarm time is reached and the audible alarm is activated, the user has the option of depressing the "snooze bar." Depressing the snooze bar silences the audible alarm for a predetermined time interval. At the end of the predetermined time interval the audible alarm resumes. Unfortunately, activation of the snooze function requires the user to awaken to silence the alarm by depressing the snooze bar. If the user is not located directly next to the clock radio, he must also arise from the bed in which he is sleeping to depress the snooze bar.
An invention relating to silent alarms is also described in U.S. Pat. No. 5,572,196 to Sakumoto et al. (hereinafter `Sakumoto`). Sakumoto discloses a device for an electronic analog timepiece equipped with a pager. Similar designs for portable timepieces containing a vibrating alarm but no paging apparatus have been proposed in U.K. Patent No. 2,205,665 to Dines, U.S. Pat. No. 5,089,998 to Rund, U.S. Pat. No. 4,456,387 to Igarashi, U.S. Pat. No. 5,023,853 to Kawata et al., U.S. Pat. No. 5,365,497 to Born, U.S. Pat. No. 5,400,301 to Rackley, U.S. Pat. No. 5,559,761 to Frenkel et al. Each of the above references disclose non-acoustical, vibrating alarm devices incorporated within a timepiece either worn on the user's wrist, placed within the user's pocket, or attached to the user's belt.
While certainly useful, each of the devices disclosed are subject to inherent disadvantages. First, conventional timepiece design requires the user to look at the machine's case and handle small knobs and buttons in order to set the proper alarm time. A watch display is necessarily small and frequently difficult to read. The small knobs and buttons provided as the user control interface on watches are also typically small and difficult to manipulate. Increasing the size of the timepiece case helps people read and handle the device, but only at the expense of obtrusiveness to the user. A person using a large vibrating alarm/timepiece in bed for waking oneself may find that the object's large size inhibits sleep.